Cooling devices and space structures

Abstract

To provide a cooling device using a pump that can sufficiently secure the degree of supercooling of a refrigerant flowing into a pump while suppressing reduction in heat radiation capacity of a heat radiation part and entry of air bubbles into the pump.SOLUTION: A cooling device 100 comprises: a pump 1 for circulating a liquid refrigerant; and a refrigerant flow passage which is formed in an annular shape with a cooler 4 for cooling a power generation apparatus such as an electronic apparatus 2 with a refrigerant and a heat radiator 5 for cooling the refrigerant being sequentially connected in the passage. The heat radiator 5 comprises a condensation flow passage 6a into which the refrigerant flowing out of the cooler 4 enters and in which the entering refrigerant flows into a plurality of branched streams to radiate heat, and a sub-cool flow passage 7a into which refrigerant which has flown out of the condensation flow passage 6a enters and in which the entering refrigerant serially flows to radiate heat.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a cooling device that cools a heat-generating device and a space structure equipped with the cooling device. [Background technology]

[0002] In space structures, heat pipes that conduct heat are embedded in the structure housing the electronic devices inside and in the panel that supports the electronic devices inside the structure. The heat generated by the electronic devices inside the structure is conducted to the heat dissipation surface of the structure via the heat pipes. The heat conducted to the heat dissipation surface is radiated from the heat dissipation surface into deep space. This cools the electronic devices. Non-Patent Document 1 describes a cooling device that uses a pump to forcibly transport a refrigerant instead of using a group of heat pipes, thereby transporting heat from an electronic device to a heat dissipation surface. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] “A Robust Two-Phase Pumped Loop with Multiple Evaporators and Multiple Radiators for Spacecraft Applications”, 47th International Conference on Environmental Systems 16-20 July 2017, ICES-2017-221 Summary of the Invention [Problem to be solved by the invention]

[0004] A group of heat pipes is used to cool electronic devices inside a space structure. In this case, the heat pipes are connected at multiple points on the heat path from the electronic device to the heat dissipation surface. This increases the contact thermal resistance between the heat pipes, reducing the cooling efficiency. In addition, the mass of the space structure increases. In order to reduce the number of connections between heat pipes, it is necessary to place the electronic devices near the heat dissipation surface of the body. Therefore, if you try to reduce the number of connections between heat pipes, it is not possible to place electronic devices that generate a lot of heat densely in the center of the body.

[0005] By using a cooling device using a pump as described in Non-Patent Document 1, it becomes possible to directly supply refrigerant to electronic equipment located at the center of the body. However, such a cooling device needs to prevent malfunction due to steam flowing into the pump. For this reason, it is necessary to flow refrigerant liquid in a supercooled liquid state into the pump. When the refrigerant liquid in a supercooled liquid state is made to flow into the pump, it is necessary to sufficiently condense the gas phase refrigerant in the heat dissipation section and further reduce the temperature of the condensed liquid phase refrigerant. When the temperature of this liquid phase refrigerant is further reduced, the temperature of the heat dissipation section is reduced. Therefore, the radiation heat dissipation efficiency to deep space is reduced in the part of the heat dissipation section where the temperature is reduced. Then, the heat dissipation capacity of the entire heat dissipation section is reduced. As a result, the degree of supercooling of the refrigerant flowing into the pump may not be sufficiently ensured. In addition, the temperature and pressure of the entire cooling device may increase, which may lead to an increase in the temperature of the heat generating device.

[0006] An object of the present disclosure is to ensure a sufficient degree of subcooling of the refrigerant flowing into the pump while suppressing a decrease in the heat dissipation capacity of a heat dissipation section and the inflow of air bubbles into the pump. [Means for solving the problem]

[0007] The cooling device according to the present disclosure comprises: A cooling device that cools heat-generating equipment mounted on the mounted device, a pump for circulating a liquid coolant, a cooler for cooling the heat generating device with the coolant, and a radiator for cooling the coolant, the coolant flow path being configured in a ring shape by sequentially connecting the pump and the coolant; The radiator is provided with a condensation flow path into which the refrigerant flowing out from the cooler flows and through which the inflowing refrigerant branches into multiple paths to dissipate heat, and a sub-cooling flow path into which the refrigerant flowing out from the condensation flow path flows and through which the inflowing refrigerant flows in series to dissipate heat. Effect of the Invention

[0008] In the present disclosure, a condensation flow path and a subcooling flow path are provided. In the condensation flow path, the refrigerant flows by branching into multiple paths. Therefore, the refrigerant with a high gas phase ratio can efficiently dissipate heat. This allows the refrigerant to dissipate heat until it becomes almost a single-phase liquid. On the other hand, in the subcooling flow path, the refrigerant flows in series. Therefore, it is possible to make the flow path longer relative to the heat dissipation area. By making the flow path longer relative to the heat dissipation area, it is possible to promote heat exchange of bubbles remaining in the almost single-phase liquid refrigerant while reducing the degree of supercooling. Since the degree of supercooling can be reduced, it is possible to suppress a decrease in the heat dissipation capacity in the heat dissipation section. Since the heat exchange of the remaining bubbles can be promoted, it is possible to suppress the inflow of bubbles into the pump. In addition, it is possible to ensure a sufficient degree of supercooling while reducing the degree of supercooling. [Brief description of the drawings]

[0009] [Figure 1] 1 is a refrigerant circuit diagram of a cooling device 100 according to a first embodiment. [Diagram 2] 1 is a refrigerant circuit diagram of a cooling device 100 according to a first embodiment. [Diagram 3] 1 is a refrigerant circuit diagram of a cooling device 100 according to a first embodiment. [Figure 4] 1 is a schematic configuration diagram of an artificial satellite 200 equipped with a cooling device 100 according to a first embodiment. [Diagram 5] FIG. 13 is a state transition diagram of a conventional cooling device. [Figure 6] FIG. 2 is a schematic diagram showing state transitions of the cooling device 100 according to the first embodiment. [Figure 7] FIG. 2 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the first embodiment. [Figure 8] FIG. 2 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the first embodiment. [Figure 9] FIG. 2 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the first embodiment. [Figure 10] FIG. 3 is a cross-sectional view of a condensation channel 6a according to the first embodiment. [Figure 11] FIG. 3 is a cross-sectional view of a condensation channel 6a according to the first embodiment. [Figure 12] FIG. 3 is a cross-sectional view of a condensation channel 6a according to the first embodiment. [Figure 13] FIG. 3 is a cross-sectional view of a condensation channel 6a according to the first embodiment. [Figure 14] FIG. 11 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the second embodiment. [Figure 15] FIG. 11 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the third embodiment. [Figure 16] FIG. 11 is a cross-sectional view of a condensation channel 6a according to a third embodiment. [Figure 17] FIG. 11 is a cross-sectional view of a condensation channel 6a according to a third embodiment. [Figure 18] FIG. 11 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the fourth embodiment. [Figure 19] FIG. 13 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the fifth embodiment. [Figure 20] FIG. 13 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the sixth embodiment. [Figure 21] FIG. 13 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the seventh embodiment. [Figure 22] FIG. 13 is a refrigerant circuit diagram of a cooling device 100 according to an eighth embodiment. [Figure 23] FIG. 13 is a refrigerant circuit diagram of a cooling device 100 according to a ninth embodiment. [Figure 24] FIG. 23 is a refrigerant circuit diagram of a cooling device 100 according to a tenth embodiment. [Diagram 25] FIG. 23 is a structural diagram of the condensation channel 6a and the subcooling channel 7a according to the eleventh embodiment. [Figure 26] FIG. 23 is a cross-sectional view of a condensation channel 6a and a heat pipe 17 according to an eleventh embodiment. [Figure 27]FIG. 23 is an exploded perspective view showing a structural example of a condenser 6, a heat pipe 17, and a condenser-side heat dissipation surface 3a according to an eleventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Embodiment 1 ***Configuration Description*** 1 to 4, the configurations of the cooling device 100 according to the first embodiment and the artificial satellite 200 which is an on-board device equipped with the cooling device 100 will be described. The artificial satellite 200 is an example of a space structure. 1 to 4, the solid arrows indicate the main flow direction of the refrigerant.

[0011] <Basic configuration> The cooling device 100 includes a closed-loop refrigerant flow path through which a refrigerant circulates, configured by sequentially connecting a pump 1, a cooler 4, and a radiator 5 with piping in a ring shape. The refrigerant is pressurized in a liquid state by the pump 1. The pressurized refrigerant receives heat from the electronic device 2 by the cooler 4 and cools the electronic device 2. After cooling the electronic device 2, the refrigerant dissipates heat by the radiator 5 and returns to the pump 1. In this manner, the refrigerant circulates through the refrigerant flow path. The cooler 4 is provided inside the electronic device 2 or in contact with the electronic device 2 so as to receive heat generated in the electronic device 2 and heat the refrigerant inside. The radiator cools the refrigerant heated by cooling the electronic device 2 in the cooler 4.

[0012] As shown in Fig. 4, the satellite 200 includes an electronic device 2 and a cooling device 100 inside the main body 21. The electronic device 2 and the cooling device 100 are supported by a frame 21a. The electronic device 2 is a device including devices for performing various missions and devices for controlling the devices and the electrical operating devices of the cooling device 100. The cooling device 100 is a device that cools the electronic device 2 by transporting heat generated when the electronic device 2 operates to the heat dissipation surface 3 and dissipating the heat to the outside of the satellite 200. The radiator 5 is provided inside the heat dissipation surface 3 provided on the outer surface of the main body 21 or in contact with the heat dissipation surface 3 so that the refrigerant heated by the cooler 4 is cooled. The heat received by the radiator 5 from the refrigerant is radiated from the heat dissipation surface 3 toward deep space outside the artificial satellite 200.

[0013] <Additional information on basic configuration> In the artificial satellite 200 orbiting a planet, the heat dissipation surface 3 may be exposed to strong solar radiation, resulting in a decrease in the amount of radiative heat dissipation or, conversely, heat reception. To prevent a decrease in the amount of radiative heat dissipation or, conversely, heat reception, it is preferable that the heat dissipation surface 3 is provided on both the south and north faces or on either the south or north face. The heat sink 5 and the heat dissipation surface 3 may be configured as a plurality of separate parts. The heat sink 5 and the heat dissipation surface 3 configured as a plurality of separate parts may be connected to the flow path in series or parallel. The cooling device 100 may be configured to be capable of switching the flow path so that the refrigerant heated in the cooler 4 flows to the radiator 5 provided on the shaded heat dissipation surface 3. With this configuration, the radiator 5 and the heat dissipation surface 3 are provided on the east or west face, and the heated refrigerant can be caused to flow from the cooler 4 to the radiator 5 on the shaded side, and heat can be dissipated from the heat dissipation surface 3.

[0014] <Characteristic composition> 1, in the cooling device 100, the radiator 5 has an internal flow path divided into a condensation flow path 6a and a subcooling flow path 7a. The refrigerant flowing out from the cooler 4 flows into the condensation flow path 6a, where the refrigerant flows into multiple branches and dissipates heat. The refrigerant flowing out from the condensation flow path 6a flows into the subcooling flow path 7a, where the refrigerant flows in series and dissipates heat. 2, the radiator 5 may include a condenser 6 and a subcooling heat exchanger 7 that is separate from the condenser 6. The condenser 6 is provided with a condensation flow path 6a. The subcooling heat exchanger 7 is provided with a subcooling flow path 7a. As shown in Fig. 3, the heat dissipation surface 3 may be divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. The condenser-side heat dissipation surface 3a may be connected to the condenser 6, and the subcooling heat exchanger-side heat dissipation surface 3b may be connected to the subcooling heat exchanger 7. Fig. 4 shows a satellite 200 in which the heat dissipation surface 3 is divided in the same manner as in Fig. 3.

[0015] The condensation flow passage 6a has a large cross-sectional area for each flow passage so that the pressure loss caused by the high-speed gas-liquid two-phase refrigerant is reduced. Furthermore, the condensation flow passage 6a is configured so that the flow passage branches into multiple paths that flow in parallel and then merge again to flow into the subcooling flow passage 7a. A refrigerant with a high liquid phase ratio and low pressure loss flows through the subcooling flow passage 7a. Therefore, the cross-sectional area of ​​the subcooling flow passage 7a is narrowed so that the refrigerant with a high liquid phase ratio can flow for a long time and exchange heat with the heat dissipation surface 3. Furthermore, the subcooling flow passage 7a is configured by closely packed flow passages connected in series. In other words, the cross-sectional area of ​​the condensation channel 6a is larger than the cross-sectional area of ​​the subcooling channel 7a.

[0016] In the condensation flow path 6a, it is necessary to dissipate a large amount of heat received as a result of the evaporation of the refrigerant liquid in the cooler 4 by condensing the refrigerant vapor back into refrigerant liquid. Therefore, it is necessary to increase the amount of heat dissipation on the heat dissipation surface 3. In the subcooling flow path 7a, it is sufficient to promote heat exchange between the supercooled liquid and the remaining bubbles. Therefore, the amount of heat dissipation from the heat dissipation surface 3 may be less than that of the condensation flow path 6a. The condensation flow passage 6a is provided in the condensation region of the radiator 5. The subcool flow passage 7a is provided in the subcool region of the radiator 5. In order to increase the amount of heat dissipated by the condensation flow passage 6a on the heat dissipation surface 3, the condensation region is made larger than the subcool region. In addition, in order to increase the amount of heat dissipated by the condensation flow passage 6a on the heat dissipation surface 3, the condensation flow passage 6a is provided more sparsely than the subcool flow passage 7a. In other words, the subcool flow passage 7a is provided more densely than the condensation flow passage 6a. In other words, the proportion of the condensation region occupied by the condensation flow passage 6a is lower than the proportion of the subcool region occupied by the subcool flow passage 7a. Therefore, the area of ​​the heat dissipation surface 3 covering the condensation flow path 6a per unit length of the condensation flow path 6a is larger than the area of ​​the heat dissipation surface 3 covering the sub-cool flow path 7a per unit length of the sub-cool flow path 7a. In other words, the ratio of the heat dissipation area to the flow path length of the condensation flow path 6a is higher than the ratio of the heat dissipation area to the flow path length of the sub-cool flow path 7a. The flow path length of the condensation flow path 6a is the flow path length from the inlet to the outlet of the condensation flow path 6a. The heat dissipation area of ​​the condensation flow path 6a is the area of ​​the heat dissipation surface 3 covering the condensation flow path 6a. The flow path length of the sub-cool flow path 7a is the flow path length from the inlet to the outlet of the sub-cool flow path 7a. The heat dissipation area of ​​the sub-cool flow path 7a is the area of ​​the heat dissipation surface 3 covering the sub-cool flow path 7a.

[0017] <Other configurations> A vapor generating unit 8 is provided in the refrigerant flow path between when the refrigerant is discharged from the pump 1 and when it flows into the cooler 4. The vapor generating unit 8 generates vapor bubbles in the refrigerant liquid discharged from the pump 1. This promotes boiling cooling in the cooler 4. The vapor generating unit 8 generates vapor bubbles using any of a heater, a laser, electromagnetic waves, ultrasonic waves, and the like. When the amount of pressure rise of the pump 1 is large, the vapor generating unit 8 may generate steam bubbles by utilizing a pressure reduction effect caused by sudden contraction and expansion of the flow path, and the like. In the vapor generating section 8, vapor bubbles can be easily generated by heating the supercooled liquid flowing out from the pump 1 to the saturated vapor temperature. However, the greater the degree of supercooling and the flow rate of the refrigerant flowing out from the pump 1, the more power consumption is required to heat it to the saturated vapor temperature. To generate vapor bubbles, it is not necessary to heat all of the flowing refrigerant liquid to around the saturated vapor temperature. It is also possible to generate vapor bubbles locally and maintain the rest of the refrigerant liquid in a supercooled state.

[0018] An accumulator 9 is provided in the refrigerant flow path so as to branch off between when the refrigerant flows out of the radiator 5 and when it is sucked into the pump 1. The accumulator 9 stores refrigerant liquid therein. The accumulator 9 adjusts the ratio of gas phase to liquid phase, pressure, and saturated vapor temperature of the refrigerant circulating through each part of the cooling device 100 according to the amount of refrigerant liquid stored therein. The accumulator 9 is configured as a mechanical type that can directly change the internal volume mechanically so that the amount of refrigerant liquid inside can be adjusted. Alternatively, the accumulator 9 is configured as a thermal type that changes the ratio of gas phase to liquid phase of the refrigerant inside the accumulator by heating and cooling.

[0019] The power source for the electronic equipment 2, pump 1, accumulator 9, steam generator 8, etc. of the artificial satellite 200 is electricity. Power is obtained from radiation received from a star such as the sun by the solar cell panel 22. The solar cell panel 22 is provided on both or either of the south and north faces of the main body 21. The orientation of the solar cell panel 22 is controlled in the east-west direction so that the light receiving surface faces the radiation from the sun. The power may be provided from a storage battery within the satellite 200. Alternatively, the power may be generated from fuel using a power generation device. The device that converts or controls the power, the storage battery, and the power generation device are included in the electronic device 2, which is a heat-generating device.

[0020] ***Explanation of Operation*** An artificial satellite 200 equipped with the cooling device 100 orbits the Earth and performs various missions in orbit using the electronic device 2. The power required for the operation of the electronic device 2 and each component of the cooling device 100, such as the pump 1, is supplied from a solar panel 22 or a storage battery or the like included in the electronic device 2. The light receiving surface of the solar panel 22 is controlled so as to be directed toward the sun. When the electronic device 2 operates and generates heat, the pump 1 starts and the refrigerant is supplied to the cooler 4 through the steam generating unit 8. Heat is transferred from the electronic device 2 to the refrigerant via the cooler 4, thereby cooling the electronic device 2. The refrigerant that receives heat from the cooler 4 flows to the radiator 5 and supplies heat to the heat dissipation surface 3, and then returns to the pump 1. The heat supplied from the refrigerant to the heat dissipation surface 3 via the radiator 5 is radiated from the heat dissipation surface 3 into deep space.

[0021] In the process in which the refrigerant circulates through the various components of the cooling device 100, when the refrigerant receives heat in the cooler 4, a part of the refrigerant liquid evaporates to become refrigerant vapor. The refrigerant vapor is cooled in the radiator 5 and returns to the refrigerant liquid. With this type of latent heat transport, high cooling capacity and cooling efficiency can be obtained. If the amount of heat dissipated by the heat dissipation surface 3 is insufficient and some of the refrigerant vapor remains in the radiator 5 and flows into the pump 1 as refrigerant vapor, the pump 1 may malfunction. In order to prevent vapor from flowing into the pump 1, the refrigerant liquid stored in the accumulator 9 is injected into each component of the cooling device 100. This increases the amount of refrigerant liquid in each component of the cooling device 100 except for the accumulator 9, and the saturated vapor pressure rises. This makes it difficult for the refrigerant liquid to evaporate in the cooler 4, and makes it easier for the refrigerant vapor to condense in the radiator 5. However, when refrigerant liquid is injected from the accumulator 9 into each component of the cooling device 100, the refrigerant liquid becomes difficult to evaporate in the cooler 4, and the saturated evaporation temperature of the refrigerant rises. This causes the temperature of the entire cooler 4 to rise, and the cooling capacity and cooling efficiency decrease. Therefore, the accumulator 9 is controlled so that the amount of refrigerant liquid inside the accumulator 9 is kept at an appropriate amount.

[0022] Furthermore, by injecting refrigerant liquid from the accumulator 9 into each component of the cooling device 100, only supercooled refrigerant liquid flows into the cooler 4. This may result in a boiling delay in which the refrigerant liquid near the heat transfer surface inside the cooler 4 does not start boiling even when the temperature exceeds the saturated vapor temperature. In this case, the temperature of the heat transfer surface rises significantly more than when boiling starts and latent heat cooling is performed, and there is a risk of uneven or insufficient cooling of the electronic device 2. In order to prevent boiling delay in the cooler 4, the steam generating unit 8 generates steam bubbles in advance and causes the refrigerant containing the steam bubbles to flow into the cooler 4. This promotes latent heat cooling using the phase change from liquid to gas phase caused by the growth of the steam bubbles in the cooler 4, preventing boiling delay.

[0023] In order to prevent bubbles that have not been condensed in the radiator 5 from flowing into the pump 1, refrigerant liquid is injected from the accumulator 9 into each component of the cooling device 100. This increases the degree of supercooling of the refrigerant liquid sucked into the pump 1. This also increases the degree of supercooling of the refrigerant liquid discharged from the pump 1. As a result, the power consumption of the steam generating unit 8, which is required to generate steam bubbles in the steam generating unit 8 and maintain the bubbles until they flow into the cooler 4, increases. Furthermore, if the area through which the supercooled liquid flows in the radiator 5 becomes large, the temperature of the heat dissipating surface 3 that exchanges heat with the supercooled liquid decreases, and the amount of heat dissipation decreases.

[0024] The cooling device 100 suppresses a decrease in the amount of heat dissipation in the radiator 5 and the inflow of air bubbles into the pump 1, while keeping the degree of supercooling of the refrigerant liquid flowing into the pump 1 low. This makes it possible to reduce the power consumption of the vapor generating unit 8. To achieve this, the cooling device 100 dissipates heat separately through the condensation flow path 6a and the subcooling flow path 7a.

[0025] The gas-liquid two-phase refrigerant that receives heat from the electronic device 2 and flows out of the cooler 4 first flows into the condensation flow path 6a. In the condensation flow path 6a, the refrigerant is cooled from a high enthalpy state close to saturated vapor to a saturated liquid state or a low enthalpy state close to the saturated liquid state from upstream to downstream. At this time, the gas-liquid two-phase state is maintained almost, so the refrigerant maintains a constant temperature. As a result, the temperature of a portion of the heat dissipation surface 3 that exchanges heat with the condensation flow path 6a is maintained at a high temperature evenly. In the configuration of FIG. 3, the portion of the heat dissipation surface 3 that exchanges heat with the condensation flow path 6a is the condenser-side heat dissipation surface 3a. In the following description, when the heat dissipation surface 3 means the heat dissipation surface 3 that exchanges heat with the condensation flow path 6a, the heat dissipation surface 3 includes the condenser-side heat dissipation surface 3a. The low-enthalpy refrigerant that flows out of the condensation flow passage 6a and is close to a saturated liquid state flows into the subcooling flow passage 7a. In the subcooling flow passage 7a, the refrigerant flows from upstream to downstream in a nearly supercooled liquid state, the temperature of which gradually decreases due to heat dissipation. This lowers the temperature of a portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow passage 7a. In the configuration of FIG. 3, the portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow passage 7a is the heat dissipation surface 3b on the subcooling heat exchanger side. In the following description, when the heat dissipation surface 3 means the heat dissipation surface 3 that exchanges heat with the subcooling flow passage 7a, the heat dissipation surface 3 includes the heat dissipation surface 3b on the subcooling heat exchanger side.

[0026] The area of ​​the heat dissipation surface 3 covering the condensation flow path 6a per unit length of the condensation flow path 6a is larger than the area of ​​the heat dissipation surface 3 covering the sub-cooling flow path 7a per unit length of the sub-cooling flow path 7a. Therefore, the high temperature area that radiates and dissipates the heat received from the condensation flow path 6a toward deep space is made large. This prevents a decrease in heat dissipation efficiency. On the other hand, the area for radiating and releasing the heat received from the subcooling channel 7a toward deep space becomes narrow. If the area of ​​this heat release surface 3 is made wider, the temperature of the refrigerant flowing through the subcooling channel 7a will decrease further. Then, in the case of the configuration of FIG. 1 or FIG. 2, the high-temperature heat release surface 3 that releases the heat received from the condensation channel 6a will be compressed, reducing the heat release efficiency. Also, the degree of supercooling of the refrigerant liquid flowing through the subcooling channel 7a will increase. However, because the area for radiating and releasing the heat received from the subcooling channel 7a toward deep space is narrow, an excessive increase in the degree of supercooling of the refrigerant liquid flowing through the subcooling channel 7a is prevented.

[0027] The condensation flow passage 6a has a short flow passage length relative to the heat radiation area on the heat radiation surface 3. However, the tube wall heat transfer between the refrigerant side of the condensation flow passage 6a and the solid of the radiator 5 or the condenser 6 is a condensation heat transfer mode accompanied by a phase change. Therefore, the heat exchange efficiency is overwhelmingly higher than the radiation heat radiation efficiency on the heat radiation surface 3, so there is almost no effect of the shortened flow passage length. The high enthalpy gas-liquid two-phase refrigerant flowing out of the cooler 4 is mostly in the low density gas phase. Therefore, the flow rate becomes fast and the pressure loss is likely to increase. However, by branching the condensation flow path 6a into multiple paths, the refrigerant flow rate per branch path becomes slower and the flow path length becomes shorter. Therefore, the pressure loss is also suppressed. As the condensation flow path 6a branches into multiple paths, drift is more likely to occur. However, when the flow rate of the refrigerant flowing through a specific branch path is low, the flow rate relative to the amount of heat dissipation is low, which results in a larger enthalpy reduction and an increased amount of condensation. A case in which the flow rate of the refrigerant flowing through a specific branch path is low is, for example, when the ratio of the gas phase to the liquid phase is high. As a result, the liquid phase ratio increases, the flow rate slows, and the pressure loss decreases. This makes it easier for the refrigerant to flow through that branch path. Therefore, even if drift is likely to occur in the condensation flow path 6a, the flow rate is automatically adjusted to reduce the drift in the flow rate.

[0028] In the subcooling flow channel 7a, the amount of heat dissipated by the refrigerant is reduced due to the narrow area of ​​the heat dissipation surface 3. However, if the residual bubbles contained in the supercooled liquid can be eliminated, the amount of heat dissipation in this area is not necessary. The subcooling flow channel 7a has a long flow channel length due to the densely arranged serial flow channels. Therefore, heat exchange between the supercooled liquid and the residual bubbles in the flow channel from upstream to downstream is promoted for a long period of time, and the residual bubbles disappear even with a small degree of supercooling. The subcooled flow passage 7a has a high ratio of low enthalpy refrigerant liquid volume and a slower flow rate of the refrigerant. Therefore, even if thin flow passages are densely connected in series to make the flow passage longer, the increase in pressure loss is suppressed.

[0029] ***Advantages of the First Embodiment*** As described above, in the cooling device 100 according to the first embodiment, the internal flow path of the heat radiator 5 is divided into the condensation flow path 6a and the subcooling flow path 7a. This increases the efficiency of heat dissipation into deep space. Furthermore, the pressure of the refrigerant in the entire cooling device 100, that is, the rise in the refrigerant temperature in the cooler 4, when the electronic device 2 is under high load is suppressed. Furthermore, even if the degree of supercooling of the refrigerant flowing into the pump 1 is low, the inflow of remaining air bubbles is prevented.

[0030] The effects of the cooling device 100 according to the first embodiment will be described with reference to FIGS. Fig. 5 is a schematic diagram showing state changes in a conventional cooling device. Fig. 6 is a schematic diagram showing state changes in the cooling device 100 according to the first embodiment. In the graphs of Fig. 5 and Fig. 6, the vertical axis indicates pressure and the horizontal axis indicates enthalpy. In the graphs of Fig. 5 and Fig. 6, the solid line X on the low enthalpy side indicates a saturated liquid curve which is the boundary between the liquid phase and two phases. Moreover, the solid line Y on the high enthalpy side indicates a saturated vapor curve which is the boundary between the two phases and the gas phase. In the graphs of Figures 5 and 6, the solid arrows indicate the state transition of the refrigerant. In the conventional cooling device 100 shown in Figure 5, the solid arrows indicate a circulation path that passes through the pump, steam generating unit, cooler, radiator, in this order, and returns to the pump again. In the cooling device 100 according to the first embodiment shown in Figure 6, the solid arrows indicate a circulation path that passes through the pump 1, steam generating unit 8, cooler 4, condensation channel 6a, and subcooling channel 7a, in this order, and returns to the pump 1 again.

[0031] Conventional cooling devices that utilize latent heat circulate the refrigerant using a pump, evaporate a portion of the refrigerant liquid in a cooler, and condense the refrigerant vapor in a radiator. In conventional cooling devices that utilize latent heat, the liquid refrigerant is pressurized by a pump to increase the amount of refrigerant circulated. If vapor flows into the pump for the refrigerant liquid, it may cause a malfunction. Therefore, it is necessary to ensure a supercooled state so that the enthalpy of the refrigerant before it flows into the pump is lower than the saturated condensation enthalpy. If the refrigerant liquid is in a supercooled state before flowing into the pump, it will also be in a supercooled state after being pressurized by the pump. Evaporation will not start unless an amount of heat equivalent to the difference between the enthalpy at the time of pressurization by the pump and the saturated condensation enthalpy is added. Therefore, heat exchange occurs in a single-phase liquid on the inlet side of the cooler. If the supercooled liquid flows into the cooler in a single-phase state, even if the refrigerant liquid near the inner wall surface of the cooler exceeds the saturated vapor temperature, bubble nuclei are not generated and grow, and boiling is delayed, resulting in a decrease in the heat transfer coefficient. As a result, cooling spots occur on the inlet and outlet sides of the cooler, and the temperature of electronic equipment attached to the inlet side of the cooler may become high.

[0032] While ensuring a supercooled state before flowing into the pump, steam bubbles are generated in advance in the steam generating section so that boiling starts immediately on the inlet side of the cooler. However, even if steam is generated in a refrigerant liquid with a high degree of supercooling, there are cases where the bubbles do not grow and the refrigerant condenses immediately. Therefore, as shown in Figure 5, it is necessary to generate steam bubbles in a state where the supercooled refrigerant liquid immediately after discharge from the pump is heated to around the saturated condensation curve in the steam generating section. However, in this method, as shown in Figure 5, it is necessary to heat the steam generating section with an amount of heat equivalent to the difference between the enthalpy at the time when the pressure is increased by the pump and the saturated condensation enthalpy. Therefore, the steam generating section consumes a lot of electricity almost equivalent to the amount of heat.

[0033] In addition, if the degree of supercooling before entering the pump is increased to prevent air bubbles from entering the pump, the refrigerant temperature before entering the pump will be lower than the saturated vapor temperature at that pressure. In other words, the enthalpy at the pump inlet will be significantly lower than the saturated liquid enthalpy. Therefore, even after the refrigerant in the radiator becomes lower than the saturated liquid enthalpy, the amount of heat dissipation required to eliminate the remaining air bubbles will increase. When the refrigerant temperature in the radiator drops, the temperature of the heat dissipation surface drops, and the amount of radiative heat dissipation decreases. Furthermore, in the liquid single-phase region below the saturated liquid enthalpy, there is almost no heat exchange due to latent heat of condensation. Therefore, a temperature gradient occurs in the refrigerant liquid near the inner wall surface of the radiator, resulting in sensible heat exchange, and the heat transfer coefficient is overwhelmingly lower than that of latent heat exchange due to condensation of the gas phase. As a result, the area of ​​almost single-phase liquid below the saturated liquid enthalpy spreads in the refrigerant flow path inside the radiator, and the amount of heat dissipation decreases in a part of the heat dissipation surface that exchanges heat with this area. As a result, the heat dissipation efficiency of the radiator decreases.

[0034] If the refrigerant flow path inside the radiator is configured to be longer, the time it takes for the refrigerant to flow through the internal flow path after it becomes equal to or lower than the saturated liquid enthalpy before flowing out of the radiator is longer. As a result, heat exchange between the refrigerant liquid and the remaining bubbles is promoted, and the remaining bubbles tend to disappear even if the degree of supercooling is low. However, in the gas-liquid two-phase region above the saturated liquid enthalpy on the upstream side, the longer flow path increases the pressure loss. If the pressure loss in the radiator is large, the flow rate of the refrigerant circulated by the pump is reduced. Also, a decrease in the pressure in the radiator relative to the cooler reduces the saturated vapor temperature, lowering the temperature of the refrigerant, and the temperature of the heat dissipation surface decreases, reducing the heat dissipation efficiency. If the accumulator is controlled to increase the overall pressure so that the refrigerant pressure in the radiator does not decrease, the refrigerant pressure inside the cooler increases. As a result, the saturated vapor temperature in the cooler increases, causing the temperature of the electronic equipment to rise.

[0035] As described above, in conventional cooling devices, when the accumulator is controlled to prevent air bubbles from flowing into the pump in order to prevent pump malfunction, there is a problem that the cooling performance and cooling efficiency of the entire cooling device are reduced.

[0036] In the cooling device 100 according to the first embodiment, the internal flow path of the radiator 5 is divided into a condensation flow path 6a and a subcooling flow path 7a. The condensation flow path 6a is assigned the role of dissipating a large amount of heat even with a small pressure loss, and the subcooling flow path 7a is assigned the role of eliminating remaining bubbles even with a small degree of supercooling. This makes it possible to improve the cooling performance and cooling efficiency of the cooling device 100 compared to the conventional technology. In the condensation flow path 6a, a high-temperature gas-liquid two-phase refrigerant flows, whose temperature does not change even if it dissipates heat. The heat dissipation area of ​​the heat dissipation surface 3 that receives heat from the high-temperature refrigerant is ensured to be large. Therefore, the amount of heat that can be radiated into deep space can be increased. In the portion of the heat dissipation surface 3 exchanging heat with the sub-cooling flow passage 7a, through which the temperature-reduced refrigerant flows in a substantially single-phase liquid state, the temperature drops and the amount of heat dissipation decreases. However, because the heat dissipation area of ​​the portion of the heat dissipation surface 3 exchanging heat with the sub-cooling flow passage 7a is narrowed, a larger heat dissipation area can be secured for the portion of the heat dissipation surface 3 exchanging heat with the condensation flow passage 6a. As a result, the amount of heat dissipation can be increased for the cooling device 100 as a whole.

[0037] In the condensation flow channel 6a, the refrigerant flows in parallel, and the flow channel length is short relative to the heat dissipation area of ​​the heat dissipation surface 3 where heat is exchanged. Therefore, even if the ratio of the gas phase, which has a low density and high speed, increases, pressure loss can be reduced. The ratio of the heat transfer area of ​​the flow channel wall surface to the heat dissipation area to deep space becomes small. However, because the condensation flow channel 6a is a two-phase gas-liquid refrigerant, the heat transfer coefficient of the flow channel wall surface is sufficiently high, so there is little impact of a decrease in heat exchange performance.

[0038] The longer the length of the subcooling flow path 7a, the longer the time for heat exchange between the supercooled liquid and the remaining bubbles, making it easier for the remaining bubbles to condense even with a low degree of supercooling. The longer the flow path length, the greater the pressure loss. However, inside the subcooling flow path 7a, there is a low-enthalpy gas-liquid two-phase flow with a high liquid phase ratio, or a supercooled liquid containing remaining bubbles. Therefore, even if the flow velocity slows, the increase in pressure loss can be suppressed. The area near the tube walls inside the subcooling flow passage 7a is almost entirely covered with liquid. This results in sensible heat exchange that creates a temperature gradient, and the heat transfer coefficient is lower than that of condensation latent heat exchange in the case of two-phase gas-liquid. However, the total tube wall area is increased by increasing the length of the flow passage and arranging the tubes densely, so the decrease in the amount of heat exchange on part of the heat dissipation surface 3 is suppressed. In the subcooling flow path 7a, the remaining bubbles can be easily eliminated even with a small degree of supercooling. Therefore, the heat dissipation area of ​​the portion of the heat dissipation surface 3 exchanging heat with the subcooling flow path 7a can be narrowed. Accordingly, the heat dissipation area of ​​the portion of the heat dissipation surface 3 exchanging heat with the condensation flow path 6a can be made wider. Therefore, the amount of heat dissipated by the cooling device 100 as a whole can be increased. Furthermore, if the degree of subcooling of the refrigerant flowing into the pump 1 is reduced, the degree of subcooling of the refrigerant flowing out of the pump 1 is also reduced. As a result, the power consumption required for preheating the refrigerant to near the saturated liquid enthalpy in order to generate vapor bubbles in the vapor generating unit 8 can be reduced.

[0039] As described above, the cooling device 100 according to the first embodiment can cool the electronic device 2 with low power consumption and high cooling capacity.

[0040] ***supplement*** An example of the structure around the condensation channel 6a and the subcooling channel 7a according to the first embodiment will be described with reference to Figs. 7 to 9, the solid arrows indicate the main flow direction of the refrigerant.

[0041] Fig. 7 shows a configuration in which a condensation flow path 6a and a subcooling flow path 7a are provided in a heat radiator 5, similar to Fig. 1. Fig. 8 shows a configuration in which a heat radiator 5 is divided into a condenser 6 and a subcooling heat exchanger 7, similar to Fig. 2. Fig. 9 shows a configuration in which a heat radiating surface 3 is divided into a condenser-side heat radiating surface 3a and a subcooling heat exchanger-side heat radiating surface 3b, similar to Fig. 3.

[0042] As shown in FIG. 7, the condensation flow path 6a is composed of a plurality of parallel flow paths through which the refrigerant flows in parallel. The subcooling flow path 7a is composed of a first flow path 71 through which the refrigerant flows in a first direction D1 and a second flow path 72 through which the refrigerant flows in a second direction D2 opposite to the first direction 71, which are repeated by bending the flow path through which the refrigerant flows in series. The interval I1 between the plurality of parallel flow paths constituting the condensation flow path 6a is wider than the interval I2 between the first flow path 71 and the second flow path 72 constituting the subcooling flow path 7a. The condensation flow path 6a is formed in a large part of the radiator 5 so that the area of ​​the portion of the heat dissipation surface 3 that dissipates the heat of the refrigerant flowing through the condensation flow path 6a to deep space is large. On the other hand, the subcooling flow path 7a is formed in a small part of the radiator 5 so that the area of ​​the portion of the heat dissipation surface 3 that dissipates the heat of the refrigerant flowing through the subcooling flow path 7a to deep space is small.

[0043] In the structural example shown in FIG. 8, the radiator 5 is divided into a condenser 6 and a subcooling heat exchanger 7. As a result, the solid parts constituting the condenser 6 and the subcooling heat exchanger 7 are discontinuous except for the flow path connection part. Therefore, the transfer of heat from the high-temperature condenser 6 to the low-temperature subcooling heat exchanger 7 is suppressed. The temperature of the part of the heat-radiating surface 3 exchanging heat with the condenser 6 is also maintained high. Therefore, the amount of heat radiated into deep space is further increased, and the temperature of the refrigerant liquid flowing in the subcooling flow path 7a of the subcooling heat exchanger 7 is easily reduced, making it easier for the remaining bubbles to disappear. As a result, the power consumption of the cooling device 100 can be reduced and the cooling capacity can be improved.

[0044] In the structural example shown in FIG. 9, the heat dissipation surface 3 is divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. The discontinuity of the solid portion suppresses the transfer of heat from the high-temperature condenser-side heat dissipation surface 3a to the low-temperature subcooling heat exchanger-side heat dissipation surface 3b. The temperature of the condenser-side heat dissipation surface 3a, which has a large area, is maintained high, further increasing the amount of heat dissipated into deep space. In addition, the temperature of the refrigerant liquid flowing in the subcooling flow path 7a that exchanges heat with the subcooling heat exchanger-side heat dissipation surface 3b is likely to decrease, and the remaining bubbles are likely to disappear. As a result, the power consumption of the cooling device 100 can be further reduced, and the cooling capacity can be improved.

[0045] An example of the structure around and inside the condensation channel 6a according to the first embodiment will be described with reference to Figs. Here, the condensation flow path 6a will be described as being provided in the condenser 6. However, the condensation flow path 6a may be provided in the radiator 5.

[0046] 10 shows a structural example in which a condensation flow path 6a is formed inside the condenser 6. In this structure, heat is transferred directly from the wall surface of the condensation flow path 6a to the condenser. Therefore, the thermal resistance from the condensation flow path 6a through the condenser 6 and the condenser-side heat dissipation surface 3a to the deep space is reduced, improving the heat exchange efficiency.

[0047] FIG. 11 shows a structural example of the condensation flow path 6a of the condenser 6, which is composed of piping. The condensation flow path 6a is supported by a piping support part 6b. The piping support part 6b is attached to a heat exchange substrate 6c. The surface of the heat exchange substrate 6c opposite to the surface to which the piping support part 6b is attached is in contact with the condenser side heat dissipation surface 3a. In this configuration, discontinuities increase in the path from the condensation flow path 6a through the condenser 6 and the condenser side heat dissipation surface 3a to dissipate heat into deep space. This increases the contact thermal resistance and reduces the heat exchange efficiency. However, the condenser 6 can be constructed without performing complex processing such as providing the condensation flow path 6a inside the condenser 6.

[0048] 12 shows a structural example in which grooves 6d are provided on the flow channel wall surface inside the condensation flow channel 6a. In this configuration, the grooves 6d increase the area of ​​the flow channel wall surface that comes into contact with the refrigerant flowing inside the condensation flow channel 6a. In addition, the flow of the boundary layer is disturbed, which promotes heat transfer and improves the heat exchange efficiency.

[0049] 13 shows a structural example in which the condensation flow passage 6a has a rectangular cross section. In this structure, the cross-sectional area of ​​the condensation flow passage 6a can be increased without increasing the thickness of the condenser 6. This reduces the flow velocity of the refrigerant flowing through each parallel flow passage, thereby reducing the pressure loss. Furthermore, in the zero-gravity or microgravity environment of space, the gas phase becomes rounded in the center of the flow path and flows more easily. Therefore, the liquid film thickness becomes thinner near the center of each side of the rectangular flow path cross section. As a result, heat exchange with the high-temperature gas phase is promoted, heat transfer is promoted, and heat exchange efficiency is improved.

[0050] 10 to 13 show structural examples of the condensation flow passage 6a. However, the subcooling flow passage 7a may be similarly constructed by replacing it with a structure in which the flow passages connected in series are closely arranged. In particular, as in FIG. 13, if the flow passage cross section of the subcooling flow passage 7a is rectangular, the flow passage length can be increased by closely arranging the subcooling flow passages 7a connected in series compared to when the flow passage cross section is circular. As a result, heat exchange with the remaining bubbles can be promoted, making it easier to eliminate the bubbles. In addition, the structural examples in Figures 10 to 13 have been described based on structural examples in which the condenser 6 and the condenser-side heat dissipation surface 3a are in contact with each other and perform heat exchange, but this may be replaced with a structure in which the condenser 6 and a portion of the heat dissipation surface 3 are in contact with each other.

[0051] Embodiment 2 The second embodiment differs from the first embodiment in that the condensation flow path 6a is provided with fins 10, which are a plurality of protrusions that branch the refrigerant. In the second embodiment, this difference will be described, and a description of the same points will be omitted.

[0052] ***Configuration Description*** The structure around condensation channel 6a according to the second embodiment will be described with reference to FIG. In FIG. 14, the solid arrow indicates the main flow direction of the refrigerant.

[0053] In the cooling device 100 according to the second embodiment, the condensation flow path 6a is configured such that a plurality of fins 10 are provided in a flow path provided on a surface along a part of the heat dissipation surface 3. The fins 10 may have a circular or polygonal structure, or a flat structure. The fins 10 are preferably structured to continuously protrude from the flow path wall surface of the condensation flow path 6a on the heat dissipation surface 3 side. With this structure, discontinuous surfaces to the heat dissipation surface 3 are reduced. Therefore, heat is easily transferred from the refrigerant flowing through the condensation flow path 6a to the heat dissipation surface 3 via the fins 10. In addition, the multiple fins 10 are preferably arranged in a staggered pattern, etc., so that the fins 10 are arranged again at the destination of the refrigerant after it collides, making it easy for the refrigerant to repeatedly collide with each other.

[0054] ***Explanation of Operation*** In the cooling device 100 according to the second embodiment, the refrigerant collides with the fins 10 in the condensation flow path 6a, branches off, and then merges again repeatedly, so that the refrigerant flows so as to spread within the flow path on the surface. Because the refrigerant flows so as to spread over the surface, the refrigerant flow speed in each part decreases, and the pressure loss decreases. In addition, when the refrigerant collides with the fins 10, the boundary layer around the fins 10 is reset, improving the heat transfer coefficient. The heat transferred from the refrigerant flowing through the condensation flow path 6a to the fins 10 is transferred to the heat dissipation surface 3 via the radiator 5 or the condenser 6, and is released into deep space.

[0055] When the gas-liquid two-phase refrigerant flowing through the condensation flow passage 6a collides with the fins 10, the gas phase and the liquid phase may be unevenly branched. In this case, the pressure loss increases on the side where there is more gas phase with low density and high velocity, making it difficult to flow. Meanwhile, the high-temperature gas phase exchanges heat for a long time and condenses, increasing the amount of liquid phase and making it easier to flow again. As a result, the refrigerant flows evenly inside the condensation flow passage 6a.

[0056] ***Effects of the second embodiment*** In the cooling device 100 according to the second embodiment, the refrigerant flows on a surface in the condensation flow path 6a, so that the pressure loss can be reduced. The refrigerant flows while colliding with a plurality of fins 10, so that heat is easily transferred to the heat dissipation surface 3 via the fins 10, and the cooling performance can be further improved. As a result, it is possible to reduce the thickness of the radiator 5 or the condenser 6, thereby making the device more compact, and the weight of the cooling device 100 can also be reduced.

[0057] Embodiment 3 The third embodiment differs from the first and second embodiments in that a porous body 11 that absorbs the liquid-phase refrigerant is provided in the condensation flow passage 6a on the flow passage wall surface opposite the heat dissipation surface 3. In the third embodiment, this difference will be described, and the description of the same points will be omitted.

[0058] ***Configuration Description*** The structure around the condensation channel 6a according to the third embodiment will be described with reference to Figs. 15 and 16, the solid arrows indicate the main flow direction of the refrigerant.

[0059] In the cooling device 100 according to the third embodiment, a porous body 11 that absorbs a liquid-phase refrigerant is provided on the wall surface of the condensation flow path 6a on the side opposite to the heat dissipation surface 3. The porous body 11 is made of a material such as foam metal, mesh, or fiber that has voids into which the refrigerant can enter.

[0060] ***Explanation of Operation*** In the cooling device 100 according to the third embodiment, in the condensation flow passage 6a, the liquid phase refrigerant flows slowly inside the porous body 11 while being captured by the porous body 11. On the other hand, the gas phase refrigerant flows quickly through the space between the porous body 11 and the flow passage wall surface on the heat dissipation surface 3 side. At this time, in the vicinity of the flow passage wall surface on the heat dissipation surface 3 side, the distance between the flow passage wall surface and the gas phase becomes closer, and the refrigerant speed in the boundary layer becomes faster. This improves the heat transfer coefficient and makes it easier to cool the gas phase.

[0061] ***Effects of the Third Embodiment*** In the cooling device 100 according to the third embodiment, the heat transfer coefficient is improved in the condensation flow path 6a, and the gas phase can be easily condensed. The improved heat transfer coefficient in the condensation flow path 6a increases the temperature of the heat dissipation surface 3, increasing the amount of heat dissipation into deep space and improving the cooling efficiency of the cooling device 100. As a result, it is possible to reduce the thickness of the radiator 5 or the condenser 6, thereby making the cooling device 100 more compact, and thus making it possible to reduce the weight of the cooling device 100. The amount of remaining bubbles flowing into the subcooling flow path 7a is also reduced, which makes it possible to reduce the size of the subcooling heat exchanger 7 and further reduce the size of the cooling device 100. In addition, the condenser 6 can be enlarged by the amount of reduction in the size of the subcooling heat exchanger 7, thereby enabling further improvement in the cooling efficiency of the cooling device 100.

[0062] ***Other configurations*** <First Modification of Third Embodiment> 17, in the cooling device 100, some of the electronic devices 2 may be installed on the surface of the condenser 6 facing the inside of the main body 21. The surface of the condenser 6 facing the inside of the main body 21 is the surface opposite to the surface to which the heat dissipation surface 3 is attached. In other words, the surface of the condenser 6 facing the inside of the main body 21 is the surface on the side on which the porous body 11 of the condensation flow path 6a is provided. This allows heat exchange between the liquid-phase refrigerant flowing through the porous body 11 of the condensation flow path 6a and the electronic device 2.

[0063] The electronic device 2 is installed in various locations inside the main body 21. Suppose that the electronic device 2 is installed near the heat dissipation surface 3, and a cooler 4 is installed to cool the electronic device 2. In this case, since it is necessary to extend a flow path from the cooler 4 to the inlet of the condensation flow path 6a, the flow path configuration of the cooling device 100 becomes long and complicated. Therefore, some of the electronic devices 2 installed near the heat dissipation surface 3 are attached to the radiator 5 or the condenser 6 and cooled by the liquid-phase refrigerant flowing through the porous body 11 of the condensation flow path 6a. This eliminates the need to make the flow path configuration long and complicated. Also, the space available for installing the electronic devices 2 inside the main body 21 is further increased. This allows the electronic devices 2 to be densely packed on the artificial satellite 200, thereby improving its functionality. Or, it allows the cooling device 100 and the artificial satellite 200 to be made smaller and lighter.

[0064] Even if the liquid-phase refrigerant flowing through the porous body 11 of the condensation flow path 6a evaporates due to heat received from the electronic device 2, the liquid-phase refrigerant is constantly supplied by the capillary force of the porous body 11. In this way, by providing the porous body 11 on the flow path wall surface of the condensation flow path 6a on the electronic device 2 side, it is possible to prevent only a portion of the condensation flow path 6a near the electronic device 2 from drying out. Therefore, the electronic device 2 can be cooled sufficiently.

[0065] Embodiment 4 The fourth embodiment differs from the first to third embodiments in that the subcool heat exchanger side heat dissipation surface 3b of the cooling device 100 is discontinuously divided into a plurality of parts. In the fourth embodiment, this difference will be described, and the description of the same points will be omitted.

[0066] In the fourth embodiment, as shown in Fig. 3, a cooling device 100 will be described using an example in which a radiator 5 includes a condenser 6 and a subcooling heat exchanger 7, and a heat dissipation surface 3 is divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. However, the cooling device 100 may have the configuration shown in Fig. 1 or 2. When the cooling device 100 has the configuration shown in Fig. 1 or 2, the subcooling heat exchanger-side heat dissipation surface 3b may be appropriately interpreted as a portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow path 7a.

[0067] ***Configuration Description*** The structure around the subcooled flow channel 7a according to the fourth embodiment will be described with reference to FIG. In FIG. 18, the solid arrow indicates the main flow direction of the refrigerant.

[0068] In the cooling device 100 according to the fourth embodiment, the subcool heat exchanger side heat dissipation surface 3b is discontinuously divided into a plurality of parts so as not to contact each other. The subcool heat exchanger side heat dissipation surface 3b is attached to the subcool heat exchanger 7 so as to exchange heat in order from the upstream to the downstream of the subcool flow passage 7a. In other words, at least the upstream side and the downstream side of the subcool flow passage 7a are provided so as to be covered by different subcool heat exchanger side heat dissipation surfaces 3b. It is preferable that the subcooler heat exchanger side heat dissipation surface 3b divided into multiple parts have a space between them or a heat insulating material is installed so that they do not directly exchange heat with each other. It is preferable that the subcooler heat exchanger side heat dissipation surface 3b which exchanges heat with the downstream side of the subcooling flow path 7a has a lower emissivity and is made of a material with high strength at low temperatures or has a highly resistant mounting part.

[0069] ***Explanation of Operation*** In the cooling device 100 according to the fourth embodiment, the temperature of the refrigerant liquid decreases from the upstream to downstream of the subcooling flow path 7a due to heat radiation from each subcooling heat exchanger side heat radiation surface 3b to deep space. The further downstream the subcooling flow path 7a, the lower the temperature of the subcooling heat exchanger side heat radiation surface 3b that exchanges heat with that region, and the amount of radiation heat radiation to deep space decreases. On the other hand, the temperature of the subcooling heat exchanger side heat radiation surface 3b that exchanges heat with the upstream side of the subcooling flow path 7a remains high, and the amount of radiation heat radiation increases. The subcooling heat exchanger side heat radiation surfaces 3b are discontinuous and insulated from each other, so that this temperature difference widens. As a result, the condensation of the remaining bubbles due to heat radiation is promoted on the upstream side of the subcooling flow path 7a. On the downstream side of the subcooling flow path 7a, the unnecessary increase in the degree of supercooling due to heat radiation after the remaining bubbles have sufficiently disappeared is suppressed, and the ratio of the disappearance of the remaining bubbles due to heat exchange between the gas phase and the liquid phase increases.

[0070] ***Effects of the fourth embodiment*** In the cooling device 100 according to the fourth embodiment, the remaining bubbles are more likely to disappear in the subcooling flow passage 7a. Also, an increase in the degree of supercooling of the refrigerant flowing into the pump 1 can be suppressed. Since the remaining bubbles are more likely to disappear, the subcool heat exchanger 7 and the subcool heat exchanger side heat dissipation surface 3b as a whole can be reduced in size. The condenser 6 and the condenser side heat dissipation surface 3a can be enlarged accordingly, improving the cooling performance of the cooling device 100. An increase in the degree of supercooling of the refrigerant flowing into the pump 1 can be suppressed. This allows the amount of preheating in the steam generating unit 8 to be reduced, reducing the power consumption of the cooling device 100 and improving the cooling efficiency.

[0071] Embodiment 5. The fifth embodiment differs from the first to fourth embodiments in that a filter 12 is provided in the subcooled flow passage 7a. In the fifth embodiment, this difference will be described, and a description of the same points will be omitted.

[0072] In the fifth embodiment, as shown in Fig. 3, a cooling device 100 will be described using an example in which a radiator 5 includes a condenser 6 and a subcooling heat exchanger 7, and a heat dissipation surface 3 is divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. However, the cooling device 100 may have the configuration shown in Fig. 1 or 2. When the cooling device 100 has the configuration shown in Fig. 1 or 2, the subcooling heat exchanger-side heat dissipation surface 3b may be appropriately interpreted as a portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow path 7a.

[0073] ***Configuration Description*** The structure around the subcooled flow channel 7a according to the fifth embodiment will be described with reference to FIG. In FIG. 19, the solid arrow indicates the main flow direction of the refrigerant.

[0074] In the cooling device 100 according to the fifth embodiment, a filter 12 is installed in the subcooling flow path 7a. The filter 12 is a porous filter, a metal foam filter, a mesh filter, a fibrous filter, or the like that has voids through which the refrigerant can pass. A plurality of filters 12 may be installed in the subcooling flow path 7a, and the refrigerant may pass through each filter 12.

[0075] ***Explanation of Operation*** In the cooling device 100 according to the fifth embodiment, when the refrigerant liquid containing the remaining bubbles passes through the filter 12 in the subcooling flow path 7a, the refrigerant liquid passes through the filter 12 easily due to capillary force, but the remaining bubbles have difficulty passing through. The remaining bubbles that cannot pass through the filter 12 exchange heat with the refrigerant liquid that flows later, condense, and become smaller or disappear. The remaining bubbles that can pass through the filter 12 are also broken down into small bubbles as they pass through and are mixed with the refrigerant liquid, facilitating heat exchange with the subsequent refrigerant liquid and making them more likely to condense. When the remaining bubbles disappear, the degree of supercooling also decreases.

[0076] ***Effects of the Fifth Embodiment*** In the cooling device 100 according to the fifth embodiment, the remaining bubbles are more likely to disappear in the subcooling flow path 7a. Also, an increase in the degree of supercooling of the refrigerant flowing into the pump 1 can be suppressed. Since the remaining bubbles are more likely to disappear, the subcooling heat exchanger 7 and the subcooling heat exchanger side heat dissipation surface 3b as a whole can be reduced. By doing so, the condenser 6 and the condenser side heat dissipation surface 3a can be enlarged to improve the cooling performance of the cooling device 100. Since an increase in the degree of supercooling of the refrigerant flowing into the pump can be suppressed, the amount of preheating in the steam generating unit 8 can be reduced, the power consumption of the cooling device 100 can be reduced, and the cooling efficiency can be improved.

[0077] Embodiment 6 The sixth embodiment differs from the first to fifth embodiments in that the cross-sectional area of ​​the subcooled flow passage 7a gradually decreases from the upstream to the downstream. In the sixth embodiment, this difference will be described, and the description of the same points will be omitted.

[0078] In the sixth embodiment, as shown in Fig. 3, a cooling device 100 will be described using an example in which a radiator 5 includes a condenser 6 and a subcooling heat exchanger 7, and a heat dissipation surface 3 is divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. However, the cooling device 100 may have the configuration shown in Fig. 1 or 2. When the cooling device 100 has the configuration shown in Fig. 1 or 2, the subcooling heat exchanger-side heat dissipation surface 3b may be appropriately interpreted as a portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow path 7a.

[0079] ***Configuration Description*** The structure around the subcooled flow channel 7a according to the sixth embodiment will be described with reference to FIG. In FIG. 20, the solid arrow indicates the main flow direction of the refrigerant. The cooling device 100 according to the sixth embodiment is configured so that the cross-sectional area of ​​the subcooling flow passage 7a gradually decreases from the upstream to the downstream.

[0080] ***Explanation of Operation*** In the cooling device 100 according to the sixth embodiment, as the subcooling flow passage 7a moves from the upstream to the downstream, the remaining air bubbles having low density gradually disappear, and the void fraction decreases. If the flow passage cross-sectional area is the same from the upstream to the downstream, the refrigerant flow velocity is faster on the upstream side than on the downstream side, resulting in a large pressure loss. The subcooling flow passage 7a is configured so that the flow passage cross-sectional area gradually narrows from the upstream to the downstream. This suppresses the increase in flow velocity on the upstream side, reducing pressure loss. Also, on the downstream side, the subcooling heat exchanger 7 can be reduced in size.

[0081] ***Effects of the sixth embodiment*** The cooling device 100 according to the sixth embodiment can suppress pressure loss on the upstream side of the subcooling flow path 7a. This can further improve the cooling performance and cooling efficiency of the cooling device 100. Also, the area of ​​the subcooling heat exchanger 7 on the downstream side of the subcooling flow path 7a can be reduced. By doing so, the condenser 6 and the condenser-side heat dissipation surface 3a can be enlarged, thereby improving the cooling performance of the cooling device 100.

[0082] Embodiment 7 The seventh embodiment differs from the first to sixth embodiments in that the subcooling flow passage 7a is provided with a plurality of deflection plates 13. In the seventh embodiment, this difference will be described, and a description of the same points will be omitted.

[0083] In the seventh embodiment, as shown in Fig. 3, a cooling device 100 will be described using an example in which a radiator 5 includes a condenser 6 and a subcooling heat exchanger 7, and a heat dissipation surface 3 is divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. However, the cooling device 100 may have the configuration shown in Fig. 1 or 2. When the cooling device 100 has the configuration shown in Fig. 1 or 2, the subcooling heat exchanger-side heat dissipation surface 3b may be appropriately interpreted as a portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow path 7a.

[0084] ***Configuration Description*** The structure around the subcooled flow channel 7a according to the seventh embodiment will be described with reference to FIG. In FIG. 21, the solid arrow indicates the main flow direction of the refrigerant.

[0085] In the cooling device 100 according to the seventh embodiment, a plurality of deflection plates 13 are provided in the subcooling flow passage 7a. In the subcooling flow passage 7a, the refrigerant flows while changing its flow direction many times due to the plurality of deflection plates 13. The deflection plates 13 change the flow direction so that the flow passage does not branch. The deflection plates 13 may be attached to the flow passage wall surface of the subcooling flow passage 7a, or may be integrated with the solid part of the subcooling heat exchanger 7 and configured with the subcooling flow passage 7a provided around it.

[0086] ***Explanation of Operation*** In the cooling device 100 according to the seventh embodiment, the refrigerant flows while changing its flow direction many times due to the multiple deflection plates 13. The amount of low-density gas phase is smaller in the subcooling flow path 7a than in the condensation flow path 6a, and the flow speed is slower. Therefore, even if multiple deflection plates 13 are provided and the flow direction is bent many times, the pressure loss is not so large. On the other hand, in the subcooling flow path 7a, the flow is bent many times by the multiple deflection plates 13, so that the secondary flow inside becomes stronger and the refrigerant liquid and the remaining bubbles are mixed. As a result, heat exchange is promoted and the remaining bubbles are easily dissipated.

[0087] ***Effects of the seventh embodiment*** In the cooling device 100 according to the seventh embodiment, the remaining bubbles are more likely to disappear in the subcooling flow path 7a. Also, an increase in the degree of supercooling of the refrigerant flowing into the pump can be suppressed. Since the remaining bubbles are more likely to disappear, the subcooling heat exchanger 7 and the subcooling heat exchanger side heat dissipation surface 3b as a whole can be reduced. By doing so, the condenser 6 and the condenser side heat dissipation surface 3a can be enlarged to improve the cooling performance of the cooling device 100. Since an increase in the degree of supercooling of the refrigerant flowing into the pump 1 can be suppressed, the amount of preheating in the steam generating unit 8 can be reduced, the power consumption of the cooling device 100 can be reduced, and the cooling efficiency can be improved.

[0088] Embodiment 8 The eighth embodiment differs from the first to seventh embodiments in that a part of the refrigerant between the pump 1 and the cooler 4 is caused to flow between the condensation channel 6a and the subcooling channel 7a. In the eighth embodiment, this difference will be described, and the description of the same points will be omitted.

[0089] In the eighth embodiment, as shown in Fig. 3, a cooling device 100 will be described using an example in which a radiator 5 includes a condenser 6 and a subcooling heat exchanger 7, and a heat dissipation surface 3 is divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. However, the cooling device 100 may have the configuration shown in Fig. 1 or 2. When the cooling device 100 has the configuration shown in Fig. 1 or 2, the subcooling heat exchanger-side heat dissipation surface 3b may be appropriately interpreted as a portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow path 7a.

[0090] ***Configuration Description*** The configuration of a cooling device 100 according to the eighth embodiment will be described with reference to FIG. In FIG. 22, the solid arrow indicates the main flow direction of the refrigerant.

[0091] The cooling device 100 according to the eighth embodiment includes a branch path that branches off from the refrigerant flow path between the pump 1 and the cooler 4 and joins the flow path between the condensation flow path 6a and the subcooling flow path 7a. The branch path is provided with a flow rate adjustment device 14 that adjusts the flow rate of the refrigerant midway. The flow rate adjustment device 14 is, for example, a valve whose opening degree can be adjusted. The branch point between the pump 1 and the cooler 4 may be either upstream or downstream of the steam generation unit 8.

[0092] ***Explanation of Operation*** In the cooling device 100 according to the eighth embodiment, when the temperature of the circulating refrigerant is likely to drop, the opening of the flow rate control device 14 is increased. This increases the amount of refrigerant flowing through the branch flow path and decreases the amount of refrigerant flowing through the main flow path on the cooler 4 side. Possible cases in which the temperature of the circulating refrigerant is likely to drop include cases in which the amount of heat generated by the heat-generating device is small or cases in which the condenser-side heat dissipation surface 3a is shaded and the heat dissipation efficiency is high.

[0093] By reducing the amount of refrigerant flowing through the cooler 4, the refrigerant liquid in the cooler 4 can easily boil even when the amount of heat generated by the heat-generating device is small, making it easier to control the temperature to a constant value. In addition, by reducing the amount of refrigerant flowing through the condensation flow path 6a, the heat transfer coefficient can be lowered, and the amount of heat dissipated from the condenser-side heat dissipation surface 3a can be reduced. The refrigerant liquid mainly flows through the branch flow path in which the flow rate control device 14 is installed. Therefore, when the refrigerant liquid and the remaining air bubbles join downstream of the condensation flow path 6a, the refrigerant liquid and the remaining air bubbles are mixed. As a result, the remaining air bubbles tend to disappear.

[0094] When the branch flow path branches off upstream of the vapor generating unit 8, the amount of refrigerant flowing through the vapor generating unit 8 decreases. Therefore, the power consumption for heating the refrigerant to the saturated liquid enthalpy in the vapor generating unit 8 decreases. When the branch flow path branches off downstream of the steam generating section 8, the supercooled refrigerant flowing out of the condensation flow path 6a is joined by the refrigerant heated to the saturated liquid enthalpy in the steam generating section 8. This warms the refrigerant flowing into the subcooling flow path 7a. This prevents the refrigerant flowing into the pump 1 from falling below the low temperature limit, causing the pump 1 to break down.

[0095] ***Effects of the eighth embodiment*** The cooling device 100 of embodiment 8 can adjust the flow rate of the refrigerant flowing through the cooler 4 and the condensation passage 6a by controlling the flow rate control device 14, without controlling the pump 1 to adjust the flow rate of the refrigerant flowing through the pump 1. When adjusting the flow rate with the pump 1, rotation speed control, power conversion, etc. may be required. Therefore, the greater the amount of power consumed by the pump 1, the more complicated the system of the cooling device 100 may become. By controlling the flow rate with the flow rate adjustment device 14, flow rate control by the pump 1 becomes unnecessary. As a result, the system of the cooling device 100 can be simplified.

[0096] In the branch passage having the flow rate control device 14, refrigerant liquid flows at a temperature substantially equal to or lower than the saturation temperature. Therefore, the remaining air bubbles are partially eliminated by merging with the refrigerant flowing out from the condensation passage 6a. As a result, even if the subcool passage 7a is short, the remaining air bubbles can be sufficiently eliminated, so the subcool passage 7a can be shortened. By shortening the subcool passage 7a, the subcool heat exchanger 7 and the subcool heat exchanger-side heat dissipation surface 3b as a whole can be reduced in size. By doing so, the condenser 6 and the condenser-side heat dissipation surface 3a can be enlarged, improving the cooling performance of the cooling device 100.

[0097] Shortening the subcooling flow path 7a can suppress an increase in the degree of supercooling of the refrigerant flowing into the pump 1. This reduces the amount of preheating in the steam generating unit 8, reducing the power consumption of the cooling device 100 and improving the cooling efficiency. In addition, by branching off a branch flow path upstream of the steam generating unit 8, the power consumption of the steam generating unit 8 can be further reduced. When the branch flow path branches off downstream of the steam generating unit 8, it becomes possible to prevent the pump 1 from breaking down by utilizing the heating in the steam generating unit 8 so that the refrigerant flowing into the pump 1 does not fall below the low temperature limit. This is effective when the amount of heat generated by the heat generating device is very small or when the condenser side heat dissipation surface 3a is in the shade and has very high heat dissipation efficiency.

[0098] Embodiment 9 The ninth embodiment differs from the first to eighth embodiments in that the gas-phase refrigerant between the condensation channel 6a and the subcooling channel 7a is returned to between the cooler 4 and the condensation channel 6a. In the ninth embodiment, this difference will be described, and the description of the same points will be omitted.

[0099] In the ninth embodiment, as shown in Fig. 3, a cooling device 100 will be described using an example in which a radiator 5 includes a condenser 6 and a subcooling heat exchanger 7, and a heat dissipation surface 3 is divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. However, the cooling device 100 may have the configuration shown in Fig. 1 or 2. When the cooling device 100 has the configuration shown in Fig. 1 or 2, the subcooling heat exchanger-side heat dissipation surface 3b may be appropriately interpreted as a portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow path 7a.

[0100] ***Configuration Description*** The configuration of a cooling device 100 according to the ninth embodiment will be described with reference to FIG. In FIG. 23, the solid arrow indicates the main flow direction of the refrigerant.

[0101] In the cooling device 100 according to the ninth embodiment, a gas-liquid separator 15 is provided between the condensation channel 6a and the subcooling channel 7a in the refrigerant channel. In the cooling device 100, an ejector 16 is provided between the cooler 4 and the condensation channel 6a in the refrigerant channel. The cooling device 100 includes a second branch channel connecting the ejector 16 to a refrigerant outlet of the gas-liquid separator 15, from which a refrigerant having a high gas phase ratio flows out. The gas-liquid separator 15 separates the gas phase from the liquid phase by utilizing an inertial force such as a centrifugal force as in a centrifugal separator, or by utilizing a capillary force as in a filter separator. The gas phase refrigerant separated by the gas-liquid separator 15 flows into the ejector 16 through the second branch passage. The gas phase refrigerant that flows into the ejector 16 through the second branch passage merges with the gas-liquid two-phase refrigerant flowing out of the cooler 4 and flows into the condensation passage 6a again. The ejector 16 is configured to draw in the gas phase separated by the gas-liquid separator 15 by contracting the gas-liquid two-phase refrigerant flowing out of the cooler 4 and utilizing the shear force due to the high-speed flow and the effect of converting static pressure into dynamic pressure and restoring static pressure again.

[0102] ***Explanation of Operation*** In the cooling device 100 according to the ninth embodiment, the gas-liquid two-phase flow flowing out of the condensation channel 6a is separated by the gas-liquid separator 15 into a refrigerant with a higher gas phase ratio and a refrigerant with a higher liquid phase ratio, and the refrigerant flows out. The refrigerant with a higher gas phase ratio is drawn in by the ejector 16. The refrigerant drawn into the ejector 16 merges with the gas-liquid two-phase refrigerant flowing out of the cooler 4 and flows back into the condensation channel 6a. On the other hand, the refrigerant with a higher liquid phase ratio flows into the subcooling channel 7a. As a result, the total refrigerant flow rate and the ratio of gas phase refrigerant increase in the condensation channel 6a. On the other hand, in the subcooling channel 7a, the total refrigerant flow rate remains the same, but the ratio of liquid phase increases. In the condensation channel 6a, the heat transfer coefficient improves due to the increase in the gas phase ratio and refrigerant flow velocity. In the subcooling channel 7a, the number of remaining bubbles decreases, making it easier for the remaining bubbles to disappear.

[0103] ***Effects of the 9th embodiment*** In the cooling device 100 according to the ninth embodiment, the amount of gas phase flowing through the condensation passage 6a increases, improving the heat transfer coefficient, thereby improving the cooling capacity and cooling efficiency of the cooling device 100. In addition, the amount of remaining bubbles flowing into the subcooling flow path 7a is reduced, so that the remaining bubbles are more likely to disappear in the subcooling flow path 7a. This makes it possible to suppress an increase in the degree of supercooling of the refrigerant flowing into the pump 1. Since the remaining bubbles are more likely to disappear, the subcooling heat exchanger 7 and the subcooling heat exchanger side heat dissipation surface 3b can be reduced in total. By doing so, the condenser 6 and the condenser side heat dissipation surface 3a can be enlarged, further improving the cooling performance of the cooling device 100. Since an increase in the degree of supercooling of the refrigerant flowing into the pump 1 can be suppressed, the amount of preheating in the steam generating unit 8 can be reduced, the power consumption of the cooling device 100 can be reduced, and the cooling efficiency can be improved.

[0104] Embodiment 10 The tenth embodiment differs from the first to ninth embodiments in that the liquid-phase refrigerant between the cooler 4 and the condensation channel 6a flows between the condensation channel 6a and the subcooling channel 7a. In the tenth embodiment, this difference will be described, and the description of the same points will be omitted.

[0105] In the tenth embodiment, as shown in Fig. 3, a cooling device 100 will be described using an example in which a radiator 5 includes a condenser 6 and a subcooling heat exchanger 7, and a heat dissipation surface 3 is divided into a condenser-side heat dissipation surface 3a and a subcooling heat exchanger-side heat dissipation surface 3b. However, the cooling device 100 may have the configuration shown in Fig. 1 or 2. When the cooling device 100 has the configuration shown in Fig. 1 or 2, the subcooling heat exchanger-side heat dissipation surface 3b may be appropriately interpreted as a portion of the heat dissipation surface 3 that exchanges heat with the subcooling flow path 7a.

[0106] ***Configuration Description*** The configuration of a cooling device 100 according to the tenth embodiment will be described with reference to FIG. In FIG. 24, the solid arrow indicates the main flow direction of the refrigerant.

[0107] In the cooling device 100 according to the tenth embodiment, a gas-liquid separator 15 is provided in the refrigerant flow path between the cooler 4 and the condensation flow path 6a. The cooling device 100 also includes a third branch flow path that connects a refrigerant outlet of the gas-liquid separator 15, from which a refrigerant with a high liquid phase ratio flows out, to a flow path between the condensation flow path 6a and the subcooling flow path 7a. A flow rate adjustment device 14 that adjusts the flow rate of the refrigerant is provided midway in the third branch flow path.

[0108] ***Explanation of Operation*** The cooling device 100 according to the tenth embodiment adjusts the flow rate of the refrigerant flowing through the condensation flow path 6a by adjusting the opening degree of the flow rate adjustment device 14 according to the amount of heat generated in the electronic device 2 and the amount of heat dissipated on the condenser-side heat dissipation surface 3a. Specifically, when the amount of heat generated in the electronic device 2 is small, the flow rate adjustment device 14 is opened to increase the amount of liquid-phase refrigerant that is not passed through the condensation flow path 6a. When the amount of heat generated in the electronic device 2 is small, the liquid-phase ratio of the refrigerant flowing out of the cooler 4 is high. Therefore, by reducing the amount of liquid phase separated by the gas-liquid separator 15 and passed through the condensation flow path 6a, the increase in the refrigerant flow rate in the condensation flow path 6a is suppressed, and the heat transfer coefficient is reduced. Furthermore, when the condenser-side heat dissipation surface 3a is shaded and the heat dissipation efficiency is increased, if the heat transfer coefficient in the condensation flow path 6a is high, the refrigerant temperature in the entire cooling device 100 will decrease. Therefore, by lowering the heat transfer coefficient in the condensation flow path 6a and reducing the amount of heat dissipation, it is possible to prevent the flow of refrigerant whose temperature is below the minimum allowable temperature into the pump 1.

[0109] In addition, when the refrigerant with a high liquid phase ratio separated in the gas-liquid separator 15 and the supercooled refrigerant containing residual bubbles flowing out of the condensation channel 6a join together, the refrigerant liquid and the residual bubbles are mixed together. As a result, some of the remaining bubbles disappear and flow into the subcooling channel 7a.

[0110] ***Effects of the 10th embodiment*** The cooling device 100 according to the tenth embodiment can adjust the flow rate of the refrigerant flowing through the condensation passage 6a by controlling the flow rate adjustment device 14, without controlling the pump 1 to adjust the flow rate of the refrigerant flowing through the pump 1. When adjusting the flow rate with the pump 1, rotation speed control, power conversion, etc. may be required. Therefore, the greater the amount of power consumed by the pump 1, the more complicated the system of the cooling device 100 may become. By controlling the flow rate with the flow rate adjustment device 14, flow rate control by the pump 1 becomes unnecessary. As a result, the system of the cooling device 100 can be simplified.

[0111] The refrigerant liquid, which is approximately at or below the saturation temperature, flows through the flow path separated by the gas-liquid separator 15 and flows to the flow rate control device 14. Therefore, some of the remaining air bubbles disappear when the refrigerant merges with the refrigerant flowing out of the condensation flow path 6a. As a result, even if the subcool flow path 7a is shortened, the remaining air bubbles can be sufficiently eliminated. By shortening the subcool flow path 7a, the subcool heat exchanger 7 and the subcool heat exchanger-side heat dissipation surface 3b as a whole can be reduced in size. By doing so, the condenser 6 and the condenser-side heat dissipation surface 3a can be enlarged, and the cooling performance of the cooling device 100 can be improved.

[0112] By shortening the subcooling flow path 7a, an increase in the degree of supercooling of the refrigerant flowing into the pump 1 can be suppressed. Therefore, the amount of preheating in the steam generating unit 8 can be reduced, which reduces the power consumption of the cooling device 100 and improves the cooling efficiency. It is possible to prevent the pump 1 from breaking down by utilizing the heating in the steam generating unit 8 so that the refrigerant flowing into the pump 1 does not fall below the low temperature limit. This is effective in cases where the amount of heat generated by the heat-generating device is very small or where the condenser-side heat dissipation surface 3a is in the shade and the heat dissipation efficiency is very high.

[0113] Embodiment 11 The eleventh embodiment differs from the first to tenth embodiments in that a plurality of heat pipes 17 are provided between the condenser 6 and the condenser-side heat dissipation surface 3a. In the eleventh embodiment, this difference will be described, and the description of the same points will be omitted.

[0114] ***Configuration Description*** The configuration of the condensation channel 6a and the subcooling channel 7a according to the eleventh embodiment will be described with reference to Figs. 25 and 27, the solid arrows indicate the mainstream direction of the refrigerant. In Fig. 26, the solid arrows indicate the mainstream direction of the gas phase refrigerant flowing inside the heat pipe 17, and the dashed arrows indicate the mainstream direction of the liquid phase refrigerant flowing inside the heat pipe 17.

[0115] In the cooling device 100 according to the eleventh embodiment, a plurality of heat pipes 17 are provided between the condenser 6 and the condenser-side heat dissipation surface 3a. The plurality of heat pipes 17 are arranged so as to spread the heat received from the refrigerant flowing through the condensation flow path 6a evenly on the condenser-side heat dissipation surface 3a. Each heat pipe 17 has a mixture of gaseous and liquid phase refrigerants in an internal sealed space. A wick 17a made of a porous material such as foamed metal, mesh, or fiber and having voids through which the refrigerant can flow is provided on the internal flow path wall surface of each heat pipe 17.

[0116] ***Explanation of Operation*** In the cooling device 100 according to the eleventh embodiment, heat released from the refrigerant flowing through the condensation passage 6 a is first transferred to a plurality of heat pipes 17 attached to the condenser 6 . In the heat pipe 17, the refrigerant liquid flowing through the wick 17a in the vicinity of the surface on which the condenser 6 is attached receives heat and evaporates. Then, the vapor flows through the space surrounded by the wick 17a, and in the wick 17a in the vicinity of the surface on which the condenser side heat dissipation surface 3a is attached, the vapor dissipates heat toward the condenser side heat dissipation surface 3a. As a result, the vapor becomes refrigerant liquid again, and flows toward the wick 17a in the vicinity of the surface on which the condenser 6 is attached due to the capillary force of the wick 17a. As described above, the refrigerant circulates repeatedly. Thereafter, the heat is received from the condenser-side heat dissipation surface 3a through the multiple heat pipes 17 that are evenly installed, and the heat is then released into deep space.

[0117] Compared to the thermal conductance due to radiation from the condenser-side heat dissipation surface 3a to deep space, the thermal conductance due to gas-liquid two-phase heat transfer in the condensation flow path 6a and the heat pipe 17 is overwhelmingly larger. Therefore, even if the condenser 6 and the condensation flow path 6a are reduced in size and the area available for mounting the multiple heat pipes 17 is reduced, heat is transferred evenly to the condenser-side heat dissipation surface 3a without a significant drop in temperature.

[0118] ***Effects of the 11th embodiment*** The cooling device 100 according to the eleventh embodiment transfers heat from the condenser 6 to the condenser-side heat dissipation surface 3a via a plurality of heat pipes 17. This makes it possible to reduce the size of the condensation flow path 6a. By reducing the condensation flow path 6a, the pressure loss of the refrigerant flowing through the condensation flow path 6a is reduced. This increases the flow rate of the refrigerant circulating through the cooling device 100, improving the cooling efficiency. Furthermore, by reducing the condensation flow path 6a, the flow path volume of the entire cooling device 100 is reduced, reducing the amount of refrigerant and making the device lighter.

[0119] For example, suppose that the cooling device 100 is mounted on a satellite 200. At this time, suppose that space debris collides with the main body 21 of the satellite 200. The condenser 6 has no portion directly attached to the condenser-side heat dissipation surface 3a, which has a large area, and the contact area is also small. Therefore, it is possible to reduce the probability that the colliding space debris will cause a hole in the condensation flow path 6a, causing the cooling device 100 to break down. Even if a hole is created in one of the heat pipes 17 due to a collision with space debris, causing a slight decrease in heat exchange efficiency, the other heat pipes 17 cover the hole. Therefore, the function of the cooling device 100 does not stop completely.

[0120] As in the past, it is also possible to cool some of the electronic devices 2 by attaching them to the surface of the heat pipes 17 on the opposite side to the condenser-side heat dissipation surface 3a inside the main body 21. Therefore, it is also possible to install the electronic devices 2 at high density inside the main body 21 to enhance the functionality of the artificial satellite 200.

[0121] Embodiment 12 In the twelfth embodiment, a case where the cooling device 100 is mounted on an on-board device other than the artificial satellite 200 will be described.

[0122] In the first to eleventh embodiments, the cooling device 100 has been described as being mounted on the artificial satellite 200. However, the cooling device 100 may be mounted on other on-board devices, not limited to the artificial satellite 200. Specifically, the cooling device 100 may be mounted on space structures other than artificial satellites, such as probes and spacecraft, or on terrestrial facilities. For example, the heat dissipation surface 3, the condenser side heat dissipation surface 3a, or the subcooling heat exchanger side heat dissipation surface 3b is replaced with a heat dissipation fin that contacts various low-temperature fluids such as air and water. This allows the electronic device 2 to be cooled in a ground facility with low power consumption and high heat dissipation capacity.

[0123] The cooling device 100 can be used regardless of the direction of gravity. Therefore, the cooling device 100 can be mounted on ground facilities in various positions. The cooling device 100 can be used for a long life without breaking down even if the position changes during use. For example, the cooling device 100 can be applied to moving equipment that is subject to inertial forces other than gravity, such as automobiles, airplanes, railway cars, and elevators, because it operates normally.

[0124] Also, for example, it is conceivable that the on-board device is an automobile driven by an engine. In this case, a heat-generating device such as an internal combustion engine of the automobile driven by the engine can be used as the object to be cooled instead of the electronic device 2. Also, the pump 1 may be attached to a rotary drive device that is driven by power obtained from the engine or an electric power device of the automobile to circulate the refrigerant.

[0125] The above describes the embodiments and modifications of the present disclosure. Some of these embodiments and modifications may be combined and implemented. Also, one or some of them may be partially implemented. Note that the present disclosure is not limited to the above embodiments and modifications, and various modifications are possible as necessary. [Explanation of symbols]

[0126] 1 pump, 2 electronic device, 3 heat dissipation surface, 3a condenser side heat dissipation surface, 3b subcooling heat exchanger side heat dissipation surface, 4 cooler, 5 heat dissipator, 6 condenser, 6a condensation flow path, 6b piping support part, 6c heat exchange substrate, 6d groove, 7 subcooling heat exchanger, 7a subcooling flow path, 8 steam generating part, 9 accumulator, 10 fin, 11 porous body, 12 filter, 13 deflection plate, 14 flow rate adjustment device, 15 gas-liquid separator, 16 ejector, 17 heat pipe, 17a wick, 21 main body, 21a frame, 22 solar panel, 100 cooling device, 200 artificial satellite.

Claims

1. A cooling device that cools heat-generating equipment mounted on the mounted device, a pump for circulating a liquid coolant, a cooler for cooling the heat generating device with the coolant, and a radiator for cooling the coolant, the coolant flow path being configured in a ring shape by sequentially connecting the pump and the coolant; The radiator is provided with a condensation flow path into which the refrigerant flowing out from the cooler flows and into which the refrigerant flows by branching into a plurality of paths to dissipate heat, and a sub-cooling flow path into which the refrigerant flowing out from the condensation flow path flows and into which the refrigerant flowing in flows in series to dissipate heat, The condensation flow path is provided in a condensation region of the radiator, The subcooling flow passage is provided in a subcooling region of the radiator, A cooling device in which the proportion of the condensation channel in the condensation region is lower than the proportion of the subcooling channel in the subcooling region.

2. A cooling device that cools heat-generating equipment mounted on the mounted device, a pump for circulating a liquid coolant, a cooler for cooling the heat generating device with the coolant, and a radiator for cooling the coolant, the coolant flow path being configured in a ring shape by sequentially connecting the pump and the coolant; The radiator is provided with a condensation flow path into which the refrigerant flowing out from the cooler flows and into which the refrigerant flows by branching into a plurality of paths to dissipate heat, and a sub-cooling flow path into which the refrigerant flowing out from the condensation flow path flows and into which the refrigerant flowing in flows in series to dissipate heat, the condensation flow path is constituted by a plurality of parallel flow paths through which the refrigerant flows in parallel, the subcooling flow path is configured by bending a flow path in which the refrigerant flows in series, so that a first flow path in which the refrigerant flows in a first direction and a second flow path in which the refrigerant flows in a second direction opposite to the first direction are alternately configured, A cooling device in which a distance between the plurality of parallel flow paths constituting the condensation flow path is greater than a distance between the first flow path and the second flow path constituting the subcooling flow path.

3. A cooling device that cools heat-generating equipment mounted on the mounted device, a pump for circulating a liquid coolant, a cooler for cooling the heat generating device with the coolant, and a radiator for cooling the coolant, the coolant flow path being configured in a ring shape by sequentially connecting the pump and the coolant; The radiator is provided with a condensation flow path into which the refrigerant flowing out from the cooler flows and into which the refrigerant flows by branching into a plurality of paths to dissipate heat, and a sub-cooling flow path into which the refrigerant flowing out from the condensation flow path flows and into which the refrigerant flowing in flows in series to dissipate heat, the radiator is provided such that the condensation flow path and the subcooling flow path are covered by a heat dissipation surface of the mounted device, A cooling device in which the area of ​​the heat dissipation surface of a portion covering the condensation flow path per unit length of the condensation flow path is larger than the area of ​​the heat dissipation surface of a portion covering the sub-cooling flow path per unit length of the sub-cooling flow path.

4. A cooling device that cools heat-generating devices mounted on the mounted device, a pump for circulating a liquid coolant, a cooler for cooling the heat generating device with the coolant, and a radiator for cooling the coolant, the coolant flow path being configured in a ring shape by sequentially connecting the pump and the coolant; The radiator is provided with a condensation flow path into which the refrigerant flowing out from the cooler flows and into which the refrigerant flows by branching into a plurality of paths to dissipate heat, and a sub-cooling flow path into which the refrigerant flowing out from the condensation flow path flows and into which the refrigerant flowing in flows in series to dissipate heat, A cooling device in which a porous body is provided on a wall surface of the condensation flow path on the side opposite to the heat dissipation side.

5. The cross-sectional area of ​​the condensation channel is larger than the cross-sectional area of ​​the subcooling channel. A cooling device according to any one of claims 1 to 4.

6. The condensation flow path is provided in a condensation region of the radiator, The subcooling flow passage is provided in a subcooling region of the radiator, The condensation region is larger than the subcooling region. A cooling device according to any one of claims 1 to 5.

7. The heat sink comprises: a condenser provided with the condensation flow path; a subcooling heat exchanger separate from the condenser and provided with the subcooling flow passage; The cooling device according to any one of claims 1 to 6, comprising:

8. the mounting device has a plurality of separate heat dissipation surfaces; The condenser and the subcooling heat exchanger are provided so as to be covered with different heat dissipation surfaces. The cooling device according to claim 7.

9. The condensation flow path is provided with a plurality of protrusions that branch the refrigerant. A cooling device according to any one of the preceding claims.

10. The heat generating device is mounted on the side of the condensation flow path where the porous body is provided. The cooling device according to claim 4.

11. The subcooling heat exchanger is provided so as to be covered with different heat dissipation surfaces on the upstream side and downstream side of the subcooling flow path. The cooling device according to claim 8.

12. 12. The cooling device according to claim 1, wherein the subcooling passage is provided with a filter having voids through which the refrigerant can pass.

13. The cross-sectional area of ​​the subcooled flow passage gradually narrows from the upstream to the downstream. A cooling device according to any one of the preceding claims.

14. The subcooling flow path is provided with a plurality of deflection plates for changing the flow direction of the coolant. A cooling device according to any one of claims 1 to 13.

15. The cooling device further comprises: a branch passage branching from a passage between the pump and the cooler in the refrigerant passage and joining a passage between the condensation passage and the subcooling passage, the branch passage having a flow rate control device provided thereon; The cooling device according to any one of claims 1 to 14, comprising:

16. a gas-liquid separator is provided between the condensation flow path and the subcooling flow path in the refrigerant flow path, and an ejector is provided between the cooler and the condensation flow path, The cooling device further comprises: a second branch flow passage connecting a refrigerant outlet from which a refrigerant having a high gas phase ratio flows out of the refrigerant outlets of the gas-liquid separator to the ejector; 16. The cooling device according to claim 1, further comprising:

17. a gas-liquid separator is provided between the cooler and the condensation flow path in the refrigerant flow path, The cooling device further comprises: a third branch passage connecting a refrigerant outlet from which a refrigerant having a high liquid phase ratio flows out of the refrigerant outlets of the gas-liquid separator to a passage between the condensation passage and the subcooling passage, the third branch passage having a flow rate control device provided thereon; 17. The cooling device according to claim 1, further comprising:

18. The condenser is covered by the heat dissipation surface via a heat pipe. The cooling device according to claim 8.

19. A space structure, which is the on-board equipment, comprising the cooling device according to any one of claims 1 to 18.

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